Chapter 20: Environmental Changes in an Ecosystem Foundations Ms. Johnson

Objectives Plants and animals within a community are dependent on each other and tend to develop a stable community in balance with their environment. Ecological succession is a natural process by which one community is replaced by another community in an orderly, predictable sequence. Certain natural processes, such as volcanic eruptions, severe weather changes, and forest fires, put stress on ecosystems and may disrupt or destroy them. Humans affect the environment by causing pollution, killing animal populations, destroying forests, and so on. These actions put stress on ecosystems and may disrupt or destroy them. Both natural and human processes that cause environmental disturbances can endanger species populations and even cause species extinction.

Vocabulary Community Succession Global warming Biodiversity Extinction

Changing Ecosystems

Biological Balance in Nature An ecosystem consists of all factors, living and nonliving, necessary to sustain a living community. ◦ Will remain stable if the factors stay constant A biological community can contain many types of plants and animals living in association with one another. ◦ Food sources, environmental conditions, balanced populations Changes in the environments can cause stress on the ecosystem and effect the community. ◦ Can be slow or sudden

Biological Balance in Nature What do you think community A might look like midway in its change to becoming like community B?

Succession Succession is a natural process by which one living community is replaced with a new community.

Succession After a fire destroys a forest, the soil becomes enriched with minerals from the remains of plants and animals that once lived there. Soon after mosses and small lichens sprout attracting insects. ◦ Eventually they die out and get replaced by larger plants (grasses, shrubs, small trees) Larger animals start to move in such as foxes and deer. As the trees grow larger a forest develops. Each new community changes the environment, making it more suitable for the next community, until one emerges that does not get replaced because it is stable (climax community).

Competition Competition for food and space is an important part of the relationships among living things in an ecosystem. Example: ◦ Moose and snowshoe hare live in same area and both eat birch tree. ◦ The moose has an advantage because it is larger. ◦ In the winter, the hare is more likely to die from starvation because of competition for limited food.

Environmental Threats That Upset the Ecosystem

Geologic Events Some geologic events can disrupt or devastate and ecosystem and can it to change. ◦ Volcanic eruptions, earthquakes, tsunamis, etc.

Geologic Events The 1980 eruption of Mount St. Helens destroyed 100,000 acres. The eruption also caused mud slides, flooding, and a blanket of volcanic ash. Aquatic animals, large animals, and birds perished. Smaller animals, like rodents, survived due to living underground. After the eruption organisms reappeared.

Climatic Changes Climate is the average condition of the atmosphere over a large region for a period of many years. ◦ Creates a wide variety of ecosystems. 18,000 years ago a large portion of the North was covered in ice and organisms such as mammoths and saber tooth tigers lived near the ice sheet. ◦ The warming climate changed the ecosystem and they went extinct.

Floods and Droughts FloodingDroughts A condition of excessive water on land. ◦ Heavy rainfall and melting ice Can upset aquatic ecosystems. Caused by a lack of precipitation for extended periods of time. ◦ Causes many plants to die removing a primary source of food. ◦ Lack of water

Storms Thunderstorms, hurricanes, tornadoes, and blizzards Thunderstorms ◦ Can ignite fires ◦ Cause hail Hurricanes ◦ Storm surge along the coast ◦ Destroy beach ecosystems Tornadoes ◦ Disrupt life in a narrow strip of land Blizzards ◦ Snow, cold, high winds, can cause organisms to freeze to death or starve

Forest Fires Forest fires destroy large areas of timber each year. ◦ Destroy trees, ecosystems, and animals Can be started naturally or by human. They play an important environmental role because ecosystems are renewed by the carbon or nutrients, succession takes place, and new plants and animals are introduced.

Human Interference 1. Pollution ◦ Pumping pollutants into the air ◦ Leads to global warming ◦ Burial and burning of garbage and toxic material ◦ Release of sewage in rivers, lakes, oceans 2. Growth and land exploitation ◦ As human population increases, we take up more land and destroy ecosystems 3. Introduction of new species ◦ When “foreign” animals are introduced they can disrupt an ecosystem ◦ Competition for food and space

Results of Environmental Change

Biodiversity Biodiversity: describes the variety of life-forms that exist. ◦ Example: there are 1,500 different fish species in the great barrier reef and 350 coral species. There are still millions of species on earth that have yet to be identified. Failure to preserve the diversity of life on earth could limit our ability to solve future problems and could limit our existence on Earth.

Biodiversity An endangered species is a plant or animal species that is close to extinction. ◦ Ex. Polar bears, pandas, tigers, blue whale, rhinos, gorillas Most of the animals that are endangered are because of humans. Reasons why: ◦ Loss of habitat ◦ Introduced species ◦ Overgrazing lands ◦ Developed areas ◦ Low gene pool diversity ◦ Predation ◦ Vegetation changes ◦ Competition ◦ Deforestation

Extinction Extinction occurs when a species dies out. ◦ Usually happens when part of the living or nonliving environment is removed. Can be caused naturally or by humans. ◦ Climate changes ◦ Floods ◦ Habitat invasions ◦ Excessive hunting ◦ Pollution of land, water, and air Dinosaurs, woolly mammoths, dodo birds, passenger pigeons

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